In a known manner, the suspension systems of motor vehicles incorporate suspension arms which comprise a ball joint at the stub axle and two linkage joints to the chassis of the vehicle, wherein these three joints together form a triangle giving the arm an overall triangular shape. These link arms are generally metallic and therefore relatively heavy.
In recent years, efforts have been made to lighten such metal arms by using composite materials, for example, as in document U.S. Pat. No. 5,267,751, which discloses a triangular suspension link arm whose three perimeter sides are formed of continuous and unidirectional longitudinal fibers impregnated with a resin and only interconnected by the three vertices of the triangle, without a central portion extending from these sides. This arm is provided with protection plates forming mounting brackets and supports rigidly fixed to the frame, i.e. not articulated.
The document WO-A1-2011/141538 teaches the production of a triangular link arm for a suspension of the type receiving a connecting ball of the stub axle and two joints for connection to the chassis, in a molded hollow shell comprising two half-shells. The arm has a rim forming a peripheral boss which defines a cavity on the perimeter of the arm, wherein each half-shell is formed by several layers of a composite material based on oriented fibers impregnated with a polymeric matrix. The shell receives in its internal cavity a metallic ductile core at the junction between the two half-shells, wherein this core is covered by the half-shells only in an intermediate zone of the shell located towards the inside of its hollow rim. One or more reinforcing layers of the arm are attached to an outer side face of its rim.
A major disadvantage of these known link arms lies in their inertia, their rigidity and their sometimes unsatisfactory resistance in use to tensile-compressive, flexural and buckling stresses and also to extreme incidental forces, to obtain a quite relative alleviation.